One year ago today, an emergency broadcast at a Boston hospital on Charles Street crackled with chilling words.

“Multiple victims. Code Red.”

“We knew this was not a drill,” said Deb Trocchi, a registered nurse at Massachusetts Eye and Ear.

Trocchi, Maureen Martinez, also a nurse, and Dr. Aaron Remenschneider were on duty at Mass. Eye and Ear when two bombs near the Boston Marathon finish line exploded, killing three people and injuring more than 250. They came to NHTI in Concord last month to tell their stories.

Their talk, sponsored by Northeast Delta Dental, was coordinated and hosted by Jack Savage of Concord, who greeted his brother at the finish line last year, 20 minutes before the first bomb exploded.

This time, on Monday, Savage is running the marathon to benefit Mass. Eye and Ear, one of eight hospitals that cared for patients the day the Boston Marathon took on a different feel, probably forever.

“I was several blocks away,” Savage told a small gathering before introducing his guests. “I felt incredibly lucky. I wondered what it was like there in the hospital.”

It was Patriots Day, a holiday unique to Boston. No school for the kids. The Red Sox had an 11 a.m. home game.

People were everywhere, walking the streets, thinking about spring, moving from Fenway Park after the game to the marathon finish line on Boylston Street.

That’s the way it had been for as long as anyone could remember, right? That’s what had always been part of the city’s charm, a sea of people all connected as one, right?

The first explosion came at 2:50 p.m., the next one 12 seconds later.

In the moments after the explosions, before caring for patients who could no longer hear or see, before the waiting room and eight exam rooms filled up with dazed looks and an eerie quiet, and before FBI agents in dark suits ran a sweep of the hospital, our three visitors said their thoughts moved to people they knew.

Seems like everyone around here knew someone who ran that day.

They worried about their friends, some of whom were avid runners. They worried about their family members, such as the pregnant sister who lives near the finish line. They worried about their colleagues who had the day off and ran in the race.

“Organized chaos,” Trocchi called it.

The TV in the hospital lobby showed the scene, less than a mile away, but no one really knew the magnitude of what had just occurred.

Then the door at the hospital entrance swung open and a young woman, the first patient, walked through. She barely said a word.

“It was an oh-my-God moment,” Martinez said. “She was stunned. She walked in alone. There was shrapnel and embedded debris all over her body. I could see what she went through, the impact of the blast.

“I’ve never seen anything like it before,” Martinez continued. “It was 10 minutes after the blasts, she walked in the doors. She couldn’t articulate what had happened.”

And so began a workday like no other for our three sources. Luckily, a shift change was occurring at the time, giving the staff an inflated number of nurses.

A lot of people who walked in were driven to Massachusetts General Hospital, connected to Mass. Eye and Ear by a bridge.

The rest had problems with vision or hearing or both. Remenschneider and his nurses described glass shards in eyes, scorched ear canals, ringing in ears, vision problems, deafness.

Remenschneider knew what to do in those cases. In others, though, he did not.

“I didn’t have a great grasp to counsel the people who were hurt like this,” he said.

The patients kept coming with their stunned looks, their blood, their confusion.

“Many were just going through the motions,” Trocchi said. “I don’t remember anyone even scrambling for their cell phones.”

The nurses and doctor said they never allowed their guards down, never let their emotions take over and the national and global impact of the tragedy to affect them.

Until later, after their shifts were over.

“When I got home, it was my family that really told me what was going on,” Martinez said. “That’s when I allowed myself to cry.”

Vicki Miller, approaching the Boston Marathon finish line a year ago today, ducked between two parked trucks and waited for a third explosion. Or, she wondered, maybe gunshots would be fired. She simply didn’t know. Her husband, Tom, two blocks away when the bombs detonated, said he felt the power, and he pushed down hard on his chest with both …

A surveillance video shows a man prosecutors say is Dzhokhar Tsarnaev placing a bomb near the finish line of the Boston Marathon, just yards from where an 8-year-old boy was killed when it exploded. A hand-scrawled confession condemning U.S. actions in Muslim countries was found on the inside wall of the boat where Tsarnaev was captured four frantic days later. …